Before cooling, the LNG tank is filled with nitrogen. During the test run, the tank will be gradually cooled from normal temperature to - 162 C. A large amount of BOG with high nitrogen content will be discharged to the torch in a short time, resulting in a great waste of resources. This paper discusses the difficulty of BOG recovery in LNG tank cooling by studying the conventional methods of LNG tank commissioning. Full nitrogen replacement and "BOG+LNG" tank cooling process are adopted before commissioning. The utilization efficiency of cold energy in receiving station is improved, the flow rate of BOG in receiving station is reduced, and the B in cooling process of LNG tank is realized. BOG zero emissions. The results showed that: (1) nitrogen in LNG tank could be fully replaced by "top intake and bottom exhaust" replacement method; (2) BOG + LNG cooling process could cool the tank, and effectively reduce the BOG flow rate in the cooling process of LNG tank to meet the processing capacity of receiving station and realize zero BOG emission in the cooling process of LNG tank. The technology of LNG tank zero emission commissioning has great reference value for the tank cooling of new storage tanks or receiving stations with the capacity of gasification and outward transportation. At the same time, "top intake bottom exhaust" nitrogen replacement, "BOG + LNG" cooling process has certain enlightenment for optimizing LNG tank design.